Formation of surface layer on cast iron cylinder bore due to nanosecond laser impulses

Abstract

The air pollution emission standards for automobiles are going to be more strict worldwide. European automotive manufacturer makes a laser treatment on the cast iron cylinder bores of the V-engine blocks. Samples of laser treated cast iron cylinder bore with lamellar graphite were investigated. Seven samples were treated with XeCl-excimerlaser, Nd-YAG laser and Yb-fiber laser sources. In order to evaluate the microstructure and grain size of the laser treated layer, scanning electron microscopic (SEM) images were taken in cross section with a SEM/focused ion beam (FIB) dual beam electron microscopes. All the samples were found to be ultra fine grained. To simulate the heating conditions during laser treatment, finite element method (FEM) simulations were made for the different lasertypes. Additional X-ray diffraction measurements showed retained austenite after laser treatment.